Neuroplasticity

Neuroplasticity (sometimes referred to as neural plasticity, neuronal plasticity, or brain plasticity) is a fascinating ability in which the nervous system modifies, changes, and adapts both structure and function throughout life and in response to experience. This process occurs by modifying or creating new synapses, which allow neurons (small cells within the nervous system) to communicate with one another. This process is critical for learning new skills and development of memory.

When young, the capacity of the brain to mold and change itself in response to different stimuli and experiences is incredibly high. As a person ages, this ability begins to slow; however, the process of synapse alteration, modification, and development never ceases. In fact, the adult human brain is adding upwards of 700 new neurons per day.

Neuroplasticity is why a stroke victim that loses function on one side of the body is capable of recovering function after the event, or why an amblyopic adult patient is capable of recovering vision. In essence, the brain never stops changing. The brain is even sometimes compared to a computer that can change or alter its circuits to improve the execution of a program.

How the Brain Works

The core component of neural tissue is a neuron. A neuron is an interesting cell made of a cell body, called the soma, which contains the critical parts of the cell like the nucleus. A neuron also contains large and small branches called axons and dendrites, respectively. These branches are critical for communication with other cells in the body (for example, muscle tissue) or other neurons. The axon is the primary carrier of signals from the soma out to other tissue or other neurons. Dendrites are used to receive signals and bring information back to the soma.

The interconnections between axons and dendrites are called synapses. Synapses transfer electrical signals (the primary method of communication in the nervous system) to chemical signals to elicit a response depending on the location in the body. Neurons constantly are creating and modifying synapses through a set of processes called synaptogenesis and synaptic pruning. Think of it this way - pathways that are commonly used are reinforced, while neural pathways that don't get much use degrade.

The Critical Period

It is well accepted that the nervous system undergoes growth and maturation at specific phases of life. The slowing of neuronal growth (termed neurogenesis) has been described as the critical period. During these unique windows of time, neural networks are highly optimized and primed for experience-driven development, which allows sensory skills to rapidly develop. It was originally thought that if a person failed to develop the required neural networks during this window of time that the opportunity for the development of the lacking skill was missed, and there was no option or chance of recovery.

Fortunately, this is only partially correct. It is true that during certain periods of development the neural system displays an enhanced capacity for growth and maturation. In addition, as a person ages, the capacity of a neural network to grow and modify is reduced. What is incorrect in the old understanding of critical periods of development is that the brain retains the capacity for synapse growth and maturation.

Neuroplasticity and Vision

The visual system is not fully developed at birth. Over the first two years of a child's life, visual experiences shape the neural architecture of the visual system. During the first four months, eye teaming begins to develop, and with this eye-hand coordination. By 8 moths depth perception is developing, and by 12 months these skills are quite robust and continue to improve. During these early months and years, an abnormal visual experience will likely inhibit the normal development of the visual system. Amblyopia, strabismus (eye turn), or pathology can significantly impact the child's visual skills.

Children, fortunately, have a highly plastic visual system - amblyopia, strabismus, and other disorders of binocular vision can often be corrected with good success if detected and treated early. Adults, however, have a less plastic visual system and will require more time and effort to overcome an abnormal visual experience in childhood.

Specific to vision, many tasks aimed at enhancing the plasticity of the visual system rely on components of perceptual learning. Perceptual learning a broad term that requires repetition of a task to improve on a certain skill. Perceptual learning may be used in concern with accommodation training, binocular tasks, monocular tasks, and more. This is a reaffirmation that practice does indeed make perfect. Vision therapy is an excellent example of how neuroplasticity is used to help enhance visual function.

Neuroplasticity Throughout Life

Neuroplasticity is enhanced throughout life by a number of factors: enriched environment (essentially, new, challenging tasks), exercise, quality diet, reduced stress, and adequate sleep.

Learning a new skill forces the brain to adapt by creating and enhancing neural pathways. Music and second language learning are excellent examples of how learning challenges the brain.

A healthy diet combined with physical exercise can help enhance neuroplasticity in multiple ways. Exercise aids the cardiovascular system decreases the risk of obesity, and helps keep the body and immune system strong--this is true at any age! Quality, balanced food and fluid intake throughout life may even have a preventive effect against late-in-life cognitive disorders, such as dementia.

Both short- and long-term meditation to reduce stress has been shown to impact functional neuroplasticity. Coupled with quality sleep, reducing stress can impact mood, memory, and neuroplasticity.